Which Earth layer is liquid and generates Earth's magnetic field?

• A. Inner core
• B. Outer core
• C. Mantle
• D. Crust

Answer: (B)

The main idea here is how Earth's magnetic field is produced by moving conductive material inside the planet. The magnetic field comes from a process called the geodynamo, which operates in the liquid part of Earth's core. This outer core is molten iron-nickel, so its material can flow in convection currents. As these conducting currents move, they generate electric currents, and those electric currents create a magnetic field. The combination of circulating, electrically conducting fluid produces and sustains Earth's magnetic field.

The inner core is solid, so it doesn’t flow like the liquid in the outer core and isn’t the place where the dynamo action primarily occurs. The mantle and crust are solid rock and do not support the kind of flowing, conductive motion needed to generate the magnetic field. So the layer that is liquid and generates Earth's magnetic field is the outer core.